Method and apparatus for mounting a brake disc with resilient biasing means

ABSTRACT

A disc brake system of the kind comprising an axially fixed hub and at least one slideable brake disc comprises a resilient device acting between the disc and the hub to control certain aspects of the movement of the brake disc during use. Despite the thermal differential arising in use between the brake disc and the central hub due to the localized heat generation of the brake system and the mass and thermal capacity differences between the hub and the brake disc, whereby the hub would be expected to provide a more satisfactory mounting, the resilient device acting between the disc and the hub to control the disc dynamics is mounted on the disc.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a method and apparatus for mounting a brakedisc in a disc brake. A particular application of the invention is to aspot-type automotive disc brake in which at least one, and preferablytwo brake discs are mounted for axial movement in use with respect to acentral drive hub which drives the discs and on which they exert abraking effect during use. Typically, the central drive hub is a wheelmounting of an automobile. Certain aspects of the invention may findapplication outside the confines of spot-type automotive disc brakes.

2. Related Art

We have established that spot-type single or multi-disc disc brakes ofthe kind comprising axially movable discs can provide significantadvantages over conventional spot-type automotive disc brakes. Theseadvantages are set out in a series of patent applications which we havefiled covering various aspects of the constructional differences betweensuch brakes and conventional automotive disc brakes.

One aspect of these constructional differences relates to the use ofresilient means acting between the one or more brake discs and therotatable mounting therefor, such resilient means being provided tocontrol certain aspects of the dynamics or movement of the brake discsduring use. Reference is made to the disclosure in WO 98/26192 for arepresentative prior disclosure in this regard, and likewise too WO98/25804. This latter disclosure concerns a disc brake system in which aplurality of leaf springs mounted on a hub and engaging the brake discapply radially-directed forces between the disc and the hub.

However, we have discovered that the mode of mounting the resilientmeans with respect to the drive hub is of significance in relation tothe effective operation of the resilient means for the brake as a whole,not to mention the resilient function itself.

As a matter of simple design principles, it is to be expected that theoptimum arrangement would be as disclosed in our above-identified priorapplications in which the resilient means is mounted on the hub andexerts its resilient or biasing effect on the disc by virtue of limitedcontact with the disc at certain well defined locations depending on theexact resilient means (or spring) design and the spring location.

Such an approach is consistent with the design principles emerging fromthe basic structure of the disc brake in which the relatively massivecentral hub provides a convenient reference base not only structurallyfor the mounting of the biasing springs, but also a relatively massiveheat sink whereby a substantial thermal gradient exists in use betweenthe brake disc with its locally-generated thermal energy and relativelylow thermal capacity, whereby thermal factors favor minimizing thenumbers of components to be subjected to frequent substantial thermalgradients, particularly components such as springs which are reliantupon thermally sensitive physical properties such as resilience.

SUMMARY OF THE INVENTION AND ADVANTAGES

However, we have discovered that despite the fact that the obviouslyapparent factors favor the adoption of the disc-mounting principles(with respect to resilient bias) disclosed in the prior art, there aresignificant and unexpected compensatory advantages in adopting thereverse approach wherein it is the disc itself which provides a mountingbase for the resilient means (for example a series ofcircumferentially-spaced springs), whereby these can be considered asexerting a resilient bias which is directed from their mounting base onthe disc to the rotatable disc-mounting hub, contrary to the teachingsof the prior art.

In embodiments of the invention there are provided resilient meansadapted to be mounted on the axially slideable brake disc in variousways and in various formats providing individual variations in ease ofconstruction and mounting.

In one embodiment the individual resilient means straddle (either as aunitary construction or as to individual resilient elements) a series ofprojecting drive keys constructed to slideably cooperate with a seriesof complementary keyways formed in the rotatable mounting hub for thebrake disc. This arrangement provides simplicity of achievingequi-spaced and likewise-balanced application of the resilient bias,without the need for cap screws or similar (potentially liable tocorrosion) mounting means.

The location of the spring or other resilient means with respect to thedisc is achieved in the embodiments by use of a spring configurationwhich is adapted to cooperate with the structure of the disc. Forexample, where a wire-format spring is adopted, then it becomes feasiblefor a structure to be adopted for that spring in which the spring isself-locating with respect to the external profile of the disc andpassing from one side of the disc to the other as necessary for locationand loading purposes. Where a leaf-spring format is adopted, it becomesfeasible for the spring to adopt the use of a pair of gripping flangesadapted to engage on opposite sides of a relevant portion of the disc.

Where a wire-format spring is adopted, a related advantage achieved iswith respect to the self-cleaning ability of the brake disc and mountinghub assembly, with respect to which the adoption of a wire spring formatprovides significantly enhanced ability to allow the escape ofparticulate and other detritus and other foreign matter whether wet ordry.

A further practical advantage arising from the mounting of the resilientmeans on the brake disc or discs relates to the dynamics of the axiallyslideable mounting of the brake disc or discs with the respect to thedrive hub or mounting means therefor. We have discovered that one resultof the mounting of the resilient means on the hub itself in priorproposals is that appreciable variations in the spring force arise fromdisc movement itself and from the adoption of two or more discs mountedin face-to-face relationship on the same hub or mounting.

By adopting the concept of mounting the resilient means on the disc ordiscs themselves an independence of spring effect is achieved since foreach spring its interaction with the disc is constant at all times andthe axial sliding movement of the disc relative to the hub hasnegligible effect on the spring interaction with this latter structuresince the resilient means slides axially with the disc. Where two ormore discs are employed, the spring effect for each is achieved by anidentical spring assembly, or a suitably proportioned spring assembly,in order to achieve an identical net spring effect.

In the embodiments of the present invention the disc brake incorporatesresilient means both in relation to the mounting of the brake discs ontheir mounting hub and in relation to the brake friction elements orpads in relation to their fixed mounting or caliper.

The resilient means are of a structure and strength chosen to be capableof, both in the case of the brake discs and in the case of the brakefriction elements, maintaining these components of the brake assembly intheir required working attitudes with respect to the structures on whichthey are mounted. In other words, the springs or resilient means for thebrake discs are constructed so as to hold the brake discs in non-tiltedworking attitudes as they rotate. Likewise, the resilient means for thefriction elements or pads maintain these latter structures in theirrequired attitudes with respect to their fixed mounting or caliper. Inboth cases, the resilient nature of the resilient means permits, underthe dynamic conditions arising during use of the vehicle and due toengine vibration and vehicle motion/road surface induced vibration andsimilar factors, a degree of movement from the defined working position(as opposed to the linear axial sliding movement needed to effectfriction element-to-disc engagement and disengagement when commencingand terminating braking) which is needed under normal conditions ofvehicle use.

In this regard, it is to be noted that the resilient means or springsused in the embodiments in relation to the friction elements formaintaining same in their normal non-tilted attitudes, differsignificantly from the springs disclosed in the above-identified WO98/25804 and WO 98/26192 specifications in which the pad springs aremere anti-rattle springs not adapted to hold the brake pads againsttilting movement, but merely to avoid rattling.

Moreover, in the embodiments of the present invention the springs forthe discs and for the pads are balanced in terms of their relativeloading applied to the discs and the pads in order to achieve thenecessary separation of same when braking is discontinued and yetholding the pads and discs against tilting during use. Thus, the springforces exerted on the pads or friction elements of the present inventionare much stronger than those needed merely to prevent rattling or noisesuppression. The spring forces are sufficient to restrain the slideablebrake pads or friction elements from moving into contact with the brakediscs in an uncontrolled manner. The use of the substantially strongerpad springs in the present embodiments assists in positioning the outerrims of the brake discs in their brake-off position for reducingresidual braking torque.

THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 shows a diagrammatic representation of the thermal and relatedmass aspects and dynamic aspects of a spot-type disc brake havingresilient means adapted to act between a relatively massive hub and apair of axially slideable brake discs;

FIGS. 2, 3, 4 and 5 show a first embodiment of the invention, namely aperspective view of a portion of a brake disc and hub assembly withassociated resilient means acting therebetween, and a plan view and aside elevation and an end elevation view respectively of the closed loopformat wire spring which constitutes the resilient means, the directionsof viewing of the spring being indicated by viewing arrows IV and V inthe usual way;

FIGS. 6, 7, 8 and 9 show a second embodiment of the invention in viewscorresponding somewhat to those of FIGS. 2-5 being a side elevation viewof the assembly, a plan view of a leaf spring forming one of tworesilient means, a side elevation view of same and an elevation viewrespectively;

FIGS. 10, 11, 12 and 13 show related views of a third embodiment of theinvention, showing the assembly, and three views of a wire-format springforming resilient means therefor which is adapted to be mounted on thebrake disc by cooperation of a wire end formation with a correspondingstructure of the disc;

FIGS. 14, 15, 16 and 17 show a modification of the embodiment of FIGS.10-13 in which the spring is adapted to straddle the disc at the innerperiphery of the latter while cooperating with the associated hub;

FIGS. 18, 19 and 20 show a leaf spring embodiment, being an assemblyview of the disc and hub and spring assembly, and a side elevation viewof the spring, and another view of the spring;

FIGS. 21, 22 and 23 show another wire-spring format embodiment, FIG. 21showing the disc and springs in assembly and FIGS. 22 and 23 showingside elevation and plan views of the springs respectively;

FIGS. 24, 25, 26 and 27 show a further wire-spring format embodiment inwhich the spring straddles an inwardly-directed drive formation on thedisc; and

FIGS. 28, 29 and 30 show a further leaf-spring-format embodiment, FIG.28 showing the disc and spring in assembly and FIGS. 29 and 30 showingplan and side elevation views of the spring respectively.

DETAILED DESCRIPTION

In FIG. 1 the thermal and related mass aspects, which will be referredto and described more fully below, are indicated by references A-E inwhich:

-   -   A refers to the Thermal Differential;    -   B refers to the Relatively Massive Hub;    -   C refers to the Spring Effect;    -   D refers to the Uniform Control of Dynamics; and    -   E refers to the Localized Spot-Type Brake Effect.

As shown in FIG. 1 a spot-type automotive disc brake system 10 comprisesrotatable brake discs 12, 14, a rotatable mounting or hub 15 for thediscs 12, 14 to permit such rotation and which is adapted to drive thebrake discs and to have exerted thereon a braking effect by the brakediscs when disc brake 10 is actuated.

Two pairs of friction elements indicated at 16, 18 and 20, 22 areadapted to frictionally engage braking surfaces on opposite sides ofbrake discs 12, 14 to effect braking on actuation of actuation means 24therefor. Brake discs 12, 14 are axially slideable in use with respectto mounting hub 15 therefor under the action of friction elements 16, 18and 20, 22 and actuation means 24 during braking.

Resilient device or means 26 is provided at circumferentially-spacedpositions around brake discs 12, 14 and is adapted to act between thebrake discs and mounting therefor at said positions. The mounting of theresilient means 26 with respect to the brake disc 12, and on same, issuch that the resilient means slides axially with the disc.

Also shown in FIG. 1 at 28 is an indication of the thermal differentialwhich exists between rotatable mounting or hub 15, which has arelatively massive construction, and the brake discs 12, 14 at whichactuation means 24 causes a localized spot-type braking effect.

Likewise shown in FIG. 1 at 30 is the uniform control of dynamics D (inrelation to axial movement of the brake discs 12, 14), which is adesideratum in relation to the function of resilient means 26 actingbetween hub 15 and brake discs 12, 14, as discussed above. In otherwords, and in particular in the case of brakes including multiple discs,it is desirable for the axial movement of the individual discs to becontrolled in a uniform manner with the springs providing a uniformeffect over the operating range of movement.

Turning now to the embodiments of FIGS. 2-27, these will be describedwith reference to the general structure shown in FIG. 1 in which therotatable mounting or hub 15 and one of the axially slideable brakediscs 12 is shown in each of the seven embodiments as part of anassembly which may comprise one, two or more discs and an associatedhub, as shown diagrammatically in FIG. 1. It is to be understood thatthe purely diagrammatic representation shown in FIG. 1 is intended to besimply a convenient reference base for the technically competent person,for purposes of description, detailed structures being shown in theremaining figures.

In the embodiments of FIGS. 2-27, the resilient means which is providedat circumferentially-spaced positions around the brake discs and whichis adapted to act between the brake disc 12 and the mounting for thebrake disc 12 at those positions itself comprises mounting means for theresilient means (in the form of a spring or springs) which is adapted tomount the resilient means at these circumferentially-spaced positions onthe brake disc or discs, so that when the resilient means is so mountedit applies a resilient bias directed from the mounting of the resilientmeans on the disc to the rotatable mounting or hub on which the disc ismounted. The resilient bias, or force acting between the disc 12 and hubis provided and generated by virtue of the resilience of the resilientmeans and deformation or bending of the resilient means. As will beunderstood by the person skilled in the art, deformation or bending ofresilient means induces stress, for example torsional stress in the casewhere the resilient means are twisted, this induced stress in theresilient means generating forces acting in the opposite direction tothe deformation or bending and tending to counter the deformation orbending.

The seven embodiments described below differ in the details whereby theresilient means is mounted on the disc.

As shown in FIG. 2, disc 12 is mounted on hub 15 by means of a series ofinwardly projecting keys or drive formations 32 of inwardly taperingformat which enter correspondingly-profiled keyways 34 or grooves formedin the hub. In this embodiment, the resilient means 26 is constituted bya wire spring 36 of generally endless loop format and having twoinwardly-directed portions defining a waist 38 adapted to fit around key32 so that the lateral side portions 40, 42 of the spring can act on theoutwardly-facing surface 44 of hub 15 at each side of the disc. Theportions 37 of the spring 36 within the waist 38 bear against the disc12 so that the spring 36 provides a force between the disc 12 and thehub 15. For this purpose, the side portions 40, 42 have smoothly-curvedcontact profiles 46, 48 with upturned ends 50, 52.

As shown in FIG. 4, spring 36 has (inside elevation) a generally convexprofile between its upturned ends 50, 52 whereby, by virtue of its wirespring construction, it exerts the required resilient effect betweendisc 12 and hub 15.

In this embodiment, four keys and corresponding springs are provided perdisc. Each spring is retained by its respective key.

Turning to the embodiment of FIGS. 6-9, in this embodiment the resilientmeans 26 is provided by a pair of leaf springs 54, 56, for each key 32on brake disc 12. The leaf springs each comprise a pair of resilientflanges 58, 60 adapted to grip the disc on opposite sides thereof and aprofiled location flange 62 adapted to cooperate with the profile of acurved recess 64, at each end of key 32, and further comprising a leafspring end portion 66 to exert the resilient force on hub 15. Thelocation flange 62 bears against the disc 12 whilst the leaf spring endportion 66 bears against the hub 15. As shown in FIG. 6, two such leafsprings 54, 56 are provided one at each side of key 32 of disc 12.

Turning now to the embodiment of FIGS. 10-13, in this embodiment thespring 70 of the resilient means is of wire-spring format and comprisesa portion 72 extending between opposite sides of the disc 12 and havingan end portion 74 at one side which engages structure at one side of thedisc and a hairpin-form spring format 76 at the other side of the discfor engagement with hub 15. The portion 72 extending between oppositesides of the disc abuts against and engages the disc 12 whilst thecurved profiled portion 71 of the hairpin portion 76 bears against thehub 15.

As previously, four such springs are provided per disc, with the hairpinspring portions 76 disposed alternately at opposite sides of the disc.

In the embodiment of FIGS. 14-17, the wire spring 80 likewise has aportion 82 extending between opposite sides of the disc, and spring endportions 84, 86 of generally linear format in plan view and convexformat in side elevation view. The end portions 84, 86 provide springforce application on hub 15 at opposite sides of the disc 12 whilst thespring is constrained by portion 82 which abuts against and engages thedisc 12.

In this embodiment four springs are provided per disc, although onlythree can be seen in FIG. 14.

In the embodiment of FIGS. 18-20, a leaf spring 90 has a leaf portion 91is of generally arcuate format (see FIG. 19) and comprises resilientflanges 92 to grip the disc 12 at opposite sides thereof. The profile ofleaf portion 91 in the unloaded condition, is linear, whereby theloading of the spring to the curved profile shown in FIG. 19 producesthe requisite spring force. When installed, the end portions 93 of thespring 90 abut and bear against the inner periphery of the disc whilstthe central portion 89 of the spring 90 bears against the outerperipheral surface of the hub 15. The spring 90 is also constrained andheld in the arcuate shape by the abutment of the end portions 93 withthe keys 32 of the disc.

In the embodiment of FIGS. 21-23, a loop-format wire spring 100 is ofgenerally bowed side elevation profile when installed on the disc 12 asshown in FIG. 22 and located between mounting formations 102 so as tohave the arcuate profile shown in FIG. 21 for resilient engagement withhub 15. The spring 100 initially has a generally linear flat naturalshape and is deformed and flexed into its bowed side elevation profilewhen installed on the disc. This bowing of the spring produces therequisite spring force. It will be appreciated though that an initiallybowed spring 100 could be used which is then further bowed wheninstalled. Disc 12 has a special profile at its inner edge,incorporating mounting formations 102 and keys 104. The mountingformations 102 comprise grooves in the disc 12 within which the ends 101of the springs 100 are engaged, thereby constraining the spring 100. Acentral portion 99 of the spring 100 abuts against an outer peripheralsurface of the hub 15.

In the embodiment of FIGS. 24-27, disc 12 has extended keys 110 aroundwhich a generally X-format (in side elevation) wire spring 112 isstraddle-mounted so that as the key enters an opening 114 (see FIG. 25)defined by double loops 116,118 and 120,122, the X-format structure ofthe spring 112 provides the resilient effect acting between the disc 12and the hub 15, as clearly shown in FIG. 24.

In the embodiment of FIGS. 28-30 the disc 12 has keys 132 which engagein keyways in the hub 15. The resilient means comprises a strip ofspring steel 130. The strip 130 in its uninstalled, unloaded conditionis generally linear as shown in FIGS. 28-30. The strip includes a numberof apertures 140 within it and at each end 136,138 there are recesses ornotches 135. In the installed loaded condition of the strip 130 it isbent and mounted within the disc 12 with the apertures 140 fitting overand straddling the keys 132 of the disc. The end of the strip 130 abutagainst one 132A of the keys 132 with the notches 135,137 engaging oneither side of that key. The three apertures 140 are equally spaced soas to receive the three other keys 132 of disc 12 and the portions ofstrip 130 therebetween extend in use, in a generally chordal directionrelative to the disc inner periphery and provide the resilient effectacting between the disc 12 and the hub 15 (not shown) which is mountedwithin the disc. It will be appreciated that the outer periphery of hub15 abuts against the portions 131 of strip 130 between apertures 140.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. The inventionis defined by the claims.

1. A disc brake system comprising: an axially movable brake disc supported on a rotatable mounting hub; a plurality of resilient devices adapted to act between said brake disc and said rotatable mounting hub at circumferentially equi-spaced positions around said brake disc, said resilient device being symmetrically mounted on said brake disc for axial movement with said brake disc independent of said mounting hub and to apply a centering and anti-tilt resilient bias force directed from said brake disc to said rotatable mounting hub.
 2. The brake disc system of claim 1 wherein said brake disc includes drive keys engaging associated drive keyways of said rotatable mounting hub, said resilient device straddling said drive keys of said brake disc.
 3. The disc brake system of claim 1 wherein said resilient device comprises at least one leaf spring having resilient flanges engaging said brake disc.
 4. The disc brake system of claim 1 wherein said spring device comprises at least one spring disposed under stress between said brake disc and said rotatable mounting hub to exert said resilient bias force therebetween.
 5. A disc brake system as set forth in claim 4 wherein said resilient device comprises a strip defining a plurality of apertures with each aperture straddling a drive key.
 6. A disc brake system as set forth in claim 5 wherein each strip extending chordally relative to said brake disc.
 7. A disc brake system comprising: a rotatable mounting hub; at least one brake disc slideable on said hub and having opposite sides and braking surfaces on said opposite sides; at least one pair of friction elements operative when actuated to frictionally engage said braking surfaces of said at least one brake disc to effect braking action of said at least one brake disc and said rotatable mounting hub; and a plurality of resilient devices attached at circumferentially spaced locations to said at least one brake disc and movable axially with said at least one brake disc relative to and independent of said rotatable mounting hub, said resilient devices acting between said at least one brake disc and said rotatable mounting hub to apply a resilient bias force directed from said at least one brake disc to said rotatable mounting hub for centering said brake disc; wherein each resilient device comprises a spring wire.
 8. A disc brake system as set forth in claim 7 wherein said spring wire defines an endless loop having two inwardly-directed portions defining a waist acting upon the brake disc and around the associated drive key of the brake disc and lateral side portions acting upon the rotatable mounting hub.
 9. A disc brake system as set forth in claim 8 wherein said side portions define upturned ends presenting curved portion abutting said mounting hub.
 10. A disc brake system as set forth in claim 7 wherein each wire spring includes an end portion engaging one side of said brake disc and a hairpin portion engaging the mounting hub on the other side of said brake disc.
 11. A disc brake system as set forth in claim 10 including a central portion between said end and hairpin portions engaging said brake disc with said hairpin portion disposed to react between said mounting hub and said disc.
 12. A disc brake system as set forth in claim 7 wherein said wire spring defines a loop having ends engaging said brake disc and bowed between said ends to engage said mounting hub.
 13. A disc brake system as set forth in claim 7 wherein said wire spring defines four double loops defining an X-shape as viewed in side elevation with an opening therebetween surrounding a drive key.
 14. A disc brake system as set forth in claim 13 wherein said X-shape includes upper arms abutting said brake disc and lower arms abutting said mounting hub. 